If you look though all other professional sports with a similar caliber as the NFL, there is no other, most important player to a team. If you were to use Brady as an example, you are looking at the face of the franchise. Not only that but the leader that the whole teams looks up to.
If Tom was to play bad, most likely they loose the game. The quarterback touches the ball more than any other player on the field.
You could try to argue the point of an elite player like Derek Jeter or David Ortiz, but again your wrong. Other players on the team still can pick up their slack. The game is not always in their hands. There are 9 other guys that swing the bat.
The New England Patriots are not as good as they were with Tom Brady, but the patriots are the most professional franchise is the NFL. They will find ways to win games and draw up game plans to fit Matt Cassel.
Bill Belichick made the decision just a week ago that Cassel would be the backup, after they had cut Matt Gutierrez. No other QB knows the patriots offense as well as Matt Cassel. Not to mention the fact that he has been learning from arguably one of the best.
The way the NFL is set up the patriots could win somewhere between 10-12 games. They only play 4 playoff teams from last year. If your thinking the patriots aren't going to be there in January you are mistaken.
In the AFC,other top favorites to make a Super Bowl appearance would be the Colts with their strong balanced offense and a better than average defense. Manning may have some rust after his surgery, but you don't need to win every game to make it and the rust won't last.
Although the Titans had just beaten the Jaguars, they also have Kerry Colins under center now with Vince Young out for 2-4 weeks. The Jaguars are a strong running team with post season experience that have a great defense and play smash mouth football.
The Steelers are also a strong team with Willie Parker healthy.
The Chargers are a great team in a weaker division, they have some questionable injuries but they are an elite team.
Romo and McNabb when healthy are the two top quarterbacks in the NFC.
In the same division still you have the Super Bowl champion, New York Giants, who won't go away easily ,Don't forget about New Orleans Saints, with Dew Brees in the driver seat. They are also explosive.
Seattle could be up there as well but you have to look at the key injuries to Nate Burleson out for the year and Branch out for 2 more weeks.
It could happen to any team, one hit, one play and your star could be gone. That's why you have back ups. They prepare to get tossed into a game whether its late in a game when their team is blowing out the competition or if your starter goes down. Its their job. Boston still believes!!